This invention relates to apparatus for and an improved method of adhering organic film to optical elements. More particularly, this invention relates to an improved stretching frame and vacuum former to be used in a process for applying molecularly-oriented, light-polarizing, organic films to optical elements without distorting the uniform direction of polarization in the film.
U.S. Pat. No. 3,051,054, issued Aug. 28, 1962 to Crandon, teaches improved bonding of light-polarizing organic films to glass substrates. Stretching frames and vacuum formers are shown generally; however, the intended use of the articles disclosed therein did not require extreme uniformity of the direction of polarization in the resultant bonded film. Therefore, the patent does not ascribe any criticality or suggest the need for a particular relationship between the shape and size of the vacuum former relative to the stretching frame but rather directs itself to a method of obtaining tenacious bonding between the polarizing film and the glass element.
My co-pending Application Ser. No. 594,989 filed July 11, 1975 describes a differentially-polarizing, optical element for use in a microscope in which there is an unusual degree of uniformity required in the direction of polarization after the film has been bonded to the optical element. U.S. Pat. No. 2,516,905, issued Aug. 1, 1952, Osterberg et al and U.S. Pat. No. 3,628,848, issued Dec. 21, 1971 to Nomarski, disclosed optical systems having elements that could be prepared by utilizing the apparatus and method of the the present invention.